Ducking - with compressor and side-chain

[JanesDaddy]

Technical question: I have mic plugged into ch 1 on mixer, insert cable to side-chain (key) on compressor. Music goes to compressor main in, with main compressor out going to a line-in channel on the mixer. The intended effect is that as I start to talk, the compressors side-chain circuit detects my voice, and fades down the music (lowers it by, say, 20dB). What's ACTUALLY happening is that the music is silent UNTIL I talk, then plays until I shut up again. So the effect is exactly the opposite of what I wanted. What's going on :?:

[X Pat Radio]

Technical question: I have mic plugged into ch 1 on mixer, insert cable to side-chain (key) on compressor. Music goes to compressor main in, with main compressor out going to a line-in channel on the mixer. The intended effect is that as I start to talk, the compressors side-chain circuit detects my voice, and fades down the music (lowers it by, say, 20dB). What's ACTUALLY happening is that the music is silent UNTIL I talk, then plays until I shut up again. So the effect is exactly the opposite of what I wanted. What's going on :?:

Not sure why you want to compress the music, since it should be already compressed. I would feed your mic into the compressor input from your mixer, then back into your mixer and forget using side-chain.

But, since you asked...

Have you tried swapping your mic and music? So your mic goes to the main in and the music goes into the side-chain?

Which compressor are you using? I know my dbx 166XL manaual shows a few examples of how to use side-chain.

[JanesDaddy]

I'm not really compressing the music per se. I'm using the compressor to automatically lower the volume of the music to a voice-over level (hence the -20dB gain) whenever I'm talking.

The compressor is a Samson S-Com Plus (http://www.samsontech.com/products/productpage.cfm?prodID=97). I normally wouldn't be attempting this 'ducking' thing, but it's new to me, and I wanted to see if I liked the effect. I could probably get the same effect with the fader on the mixer :wink: but where's the fun in that!

I tried all permutations and combinations of wiring (the Insert cable, for example, has a 'ring' and 'tip' label, which I tried plugging into the side-chain in/out in a different order). Logically, the instructions are straightforward. Just in practise it doesn't work as expected.

I'll look up the dbx instruction manual (ftp://ftp.dbxpro.com/pub/PDFs/Manuals/English/dbx166XLManualA2.pdf) online. These units are very similar, so the instructions should be the same.

[guscave]

check to see if your compressor has an "auto gain" button. If it does turn it off. Also try adjusting the threshold to ratio amount, it might be set too high or too low.

[JanesDaddy]

... try adjusting the threshold to ratio amount, it might be set too high or too low.
So, after a day of not thinking about it, I spent another couple of hours experimenting just now, and finally got the music to go down by about 15-18dB (enough to still hear a little music, but not too much). The problem, as you hinted, was the Threshold and Ratio. The wiring was correct all along.

I had to reduce the volume of the music going into the compressor (too high and nothing would happen). Normally, my Threshold is set at -20dB and the Ratio at about 5:1. I accidentally tried turning the Threshold all the way to -40dB (totally counter-clockwise), and the ratio to almost infinity. That seemed to do it, EXCEPT...

Now, when I'm recording, I get the music on channel 1 (where my mic is), but no voice in the recording at all. I can mute channel 5 (where the music is SUPPOSED to be coming back in to the mixer) and it makes no difference.

So, I'm slightly closer to the whole answer, but not all the way yet. :?

[JanesDaddy]

After more experimenting, I found this at the Alesis web site (http://www.alesis.com/support/faqs/masterlink_comp_app.html)
To make the compressor into a ducker, plug the source into the inputs and plug the trigger into the sidechain. The Sidechain return (the ring connection) isn't used in this example. In the example below, the sound of a radio announcer's voice will automatically turn the music down when he speaks and it will slowly fade back in after he stops:
When I removed the side-chain return (marked ring), the music returned to channel 5 on the mixer [which is as expected], but now (obviously) there's no way for the vocal to return to channel 1 - I just unplugged it! What now?

[JanesDaddy]

...there's no way for the vocal to return to channel 1 - I just unplugged it! What now?
After sleeping on it overnight, the answer was obvious, instead of using the mixer's Insert feature (like all the instructions tell you), I simply used an Aux Send. This has the advantage of leaving my mic's Insert free to connect to another channel on the compressor (which I wanted to do, to produce beautiful vocals!), AND I can use ANY of the mixer's channels to do the ducking, not just the one vocal channel (a co-host's, for example).
I guess I just needed to think out loud. :D Thanks to Andrew for his effort.